1. Field of the Invention
This invention relates to an input device for electronic apparatus.
2. Description of the Prior Art
The recent advancement in the performance of electronic apparatus such as electronic calculators brought about by the progress of the large-scale integrated circuits is resulting in the increase in number of the key switches constituting a part of the input device. Therefore, for example in calculators capable of functional calculations, a compact structure is generally achieved by the use of double- or triple-function keys wherein each key performs plural functions by combinations with other keys.
Also the increase in number of keys leads to the increase in number of input/output ports of the large-scale integrated circuit, and the use of the above-mentioned double- or triple-function keys has been an effective measure for preventing such increase. However multiple functions represented by a single key are difficult to learn for the users and inevitably lead to complicated and easily mistakable operations.